Try a sub a third in the back

I’ll share something I stumbled upon in the off chance it transforms your listening experience as it did mine. I purchased a rel s/510 while they were on sale to replace a lesser sub. First, the sub is remarkable. I thought it would just add bass extension. I had no idea it would improve the sound stage so much. But now I had 3 subs with absolutely no space in the front of the room to place the third. I planned to sell it. If you like to tinker like me with your system, you probably would have had the same thought I finally did: connect the third sub for the hell of it. In part, the idea was inspired by the long and very good article someone on here linked to about subs: that talks about putting a sub at the back of the room for HT. The lower the frequency, the more non directional the sound. So, having a sub behind me should be okay in a two-speaker setup. The worst that might happen, I thought was that I might shake my house off it’s foundation. But what happened was absolutely unexpected. The sound in the room became amazingly three dimensional. This is not hyperbole. I have a good system and especially with the new Rel sub, there was good width, height, and depth to the sound. But the effect of adding the third sub was to double or triple the depth into the room. I didn’t believe it so I turned the rear sub on and off, repeating the songs. I’ve done this for a week because sometimes new experiences don’t hold up over time—a product of wishful thinking. This one has lasted. I will describe the change this way. Without the rear sub, the vocals were centered, other instruments were placed around the front of the room—some further away than others. Adding the rear sub stretched the centered voice in front of me from 2d to 3D, like someone was in the room, or better, I was in the vocalist’s room. Imagine taking a photo of the singer and stretching it into a 3-dimensional figure in front of you. It’s like that. Although my previous system had good depth before, with the third sub it sounded like I was swimming in the music. there was an exceptional separation of the instruments around and over me not just in front of me. I won’t go on because results will vary. But if you like to tinker and you have a third sub in the house, give it a go. I hope it turns out as holographically for you as it did for me. (Details: I connected the Rel using the line in from my power amp and two RCA outs on my Dac (it also has XLR outs that I use) to connect the other subs.)


I agree with you pennpencil,

I am using (4) JL Audio F-113 subs in the corners of the room. Each sub can be calibrated based on its location and my sitting position. I also have the JL Audio Electronic crossover the CR-1 which blends the whole thing together.

Once the bass is dialed in everything else locks into place.



“For the best imaging when you have more than two subwoofers, the other subs should be placed so the listeners are equal or greater distance from the mains and at a somewhat lower sound pressure level. In my experience, a 30-50 millisecond delay works well to keep the image up front. Also, having all the extra subwoofers combined, play slightly lower in sound level than the main/front subs alone was the best for music.”

And from the link above:


Moving from one subwoofer to two makes a very noticeable difference in the performance of the system. Going from two to four was always an improvement, sometimes for certain seating positions more than others. Often the improvement was so subtle, that it would probably not be worth doubling your budget for subwoofers.


Third test:

We added a second subwoofer in the same position behind us. The least effect was in the chair in the center of the room, but the bass was considerably cleaned up in that position, and to a greater degree in all other positions. Front to back frequency balance was much smoother.

Fourth test:

We had two subwoofers in the two front corners. All the front to back ringing came back with a vengeance. Side to side was consistent, but consistently bad. Very noticeable excitation of the front to back room resonance.

@oldhvymec That .  .  .  sub . . . what  . . . planet? . . . back to kindergarten for me.


I took the advise from the REL tech and added my second T/9i on the back wall on the opposite diagonal corner. Dialed in the settings for volume and crossover frequency based on the room dimensions and WOW! Ask for help from REL, they know what they are doing.